The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Two nuns slain in Mississippi home

Two nuns who worked as nurses and helped the poor in rural Mississippi were found slain in their home, perhaps victims of a break-in and vehicle theft, officials said Thursday.

Authorities would not say if they have a suspect or what kind of vehicle was missing from the home. They also did not release a cause of death, but the Reverend Greg Plata said police told him the sisters were stabbed.

The nuns were identified as Sister Margaret Held and Sister Paula Merrill, both 68. Their bodies were taken to a state crime lab for autopsies.

The women, both nurse practitioners, were found Thursday morning when they didn't report to work at a nearby clinic, where they provided flu shots, insulin and other medical care for children and adults who couldn't afford it.

``They were two of the sweetest, most gentle women you can imagine. Their vocation was helping the poor,'' said Plata, who oversees a 35-member Catholic church the sisters attended.

Maureen Smith, a spokeswoman for the Catholic Diocese of Jackson, said there were signs of a break-in at the home.

Authorities didn't release a motive and it wasn't clear if the nuns' religious work had anything to do with the slayings.